Mirrored crops and white gardens, or: Making the planet more reflective

Might the cultivation of “shiny crops” be a good way to reflect solar energy back into space – thus helping cool the surface of the planet in the fight against global warming?

These “fields of shiny crops,” the Guardian reported this morning, “could send more of the sun’s heat back into space, and even reverse temperatures in parts of the world.”“Encouraging farmers to grow shinier crops” would presumably be most successful “in agricultural and forestry areas,” we read, “where the land surface is already under significant human influence.”How exactly this would be done is fascinating – because it’s about increasing the surface area of each individual plant, not growing tentacular cacti of living silver, or mirrored roses in rows unfolding across remote landscapes. Rather than metallic plantlife, that is, or cyborg-plants, we just need denser, lighter colored leaves. For instance, “an extra-hairy variety of soya bean… reflects about 5% more sunlight than normal,” and “growing broadleaf varieties of trees instead of conifers” could be enough to reflect several percentage points more. And there is an architectural side to all this: “Other scientists have suggested different ways to cool the planet [such as] painting roads, roofs and car parks white.”

20 thoughts on “Mirrored crops and white gardens, or: Making the planet more reflective”

The crops idea seems misguided, because it isolates albedo from the carbon-fixing activity of photosynthesis. It’s like the misguided notion that trees cause global warming that some irresponsible scientists have been floating.

White roofs are a no-brainer, though, especially holistically– they reduce cooling costs in houses, esp. compared to the black asphalt shingles that suck in heat bake most upstairs. So you get a double positive effect. Even semi-reflective dark tin is better than the heatsuckers now an industry standard.

James Lovelock– the “Gaia Hypothesis” guy, who is smart but a little off– suggests rocketing giant reflective surfaces into low orbit to reflect sun. Maybe this could work, esp. in the Arctic, but it seems so bizarre to be at such a point.

Also….. white roads? I can’t imagine the glare wouldn’t be horrible, and they wouldn’t stay white for any amount of time at all, seeing as rubber peels off every single tire that passes, as well as oil and other automobile secretions.

I’ve always thought the amount of pavement on the earth must be contributing to global warming. Barring that, it certainly screws up the microclimates of our cities… Couldn’t there be some kind of cumulative effect going on there?

I suspect it’s a better idea to have parking lots paved with those hollow paving blocks for the grass to grow through than to paint them all white, though. (Although, that can’t be good for our aquifers)

And a grassy or flowery roof is better – and prettier – than a white one.

That white hosta would look pretty spectacular on the roof, though, too…

Or we can try to genetically transform cows to fart cool air? As global warming awareness becomes mainstream, ideas to combat it become more and more ridiculous. Just don’t try to actually change your way of life…

I have this sudden strange and beautiful image of a group of eco-guerillas on the prowl with cans of whitewash painting the tops of everything white – cars, buildings, slow moving pedestrians… Kinda like The Train where the resistance fighters whitewash the tops of train cars carrying art works.

This makes me think of another story about white in nature: The discovery last year of the tiny Cyphochilus beetle in Southeast Asia. Its shell is whiter than most things found in nature and scientists found that it was covered with layers of ultra-thin scales that were 10 times thinner than human hair, but incredibly strong. They think the white shell evolved to blend in with an indigenous white fungus. An article in the BBC news said they were looking for ways to replicate the construction to enhance the whiteness of synthetic objects, like papers, plastics, white-light displays.

If reflective plants and lighter surfaces are implemented, nothing about global warming would change. Sure, the solar radiation is kept from reaching the earth’s surface, but this just increases the radiation in the atmosphere trapped in by greenhouse gases. This is probably the stupidest idea I’ve heard all day. Can anyone back me up here?

Green roofs DEFINITELY better than white roofs, as plants sequester carbon in addition to reducing albedo. Also better for the hydrological cycle as rainfall and meltwater enter the receiving bodies (streams, &c.) more slowly, like they do in natural systems.

For the same reason, exurban escape, permeable parking areas and back alleys, like those paving bricks with grass growing in them, are actually better for our aquifers than quickly-flushed pavement. Additionally, microbes in the soil can break down a lot of the hydrocarbons from inevitable under-car drips, which is better than having them accumulate on paved surfaces then flush into receiving waters via storm drains with the next big rainfall. (That’s why streets are often slippery in the first rain after a dry spell.)

My first comment to a post on BLDGBLOG, which I love. Perhaps obviously, I come at architecture and landscape from an ecological point of view, but the more abstract or pure aspects entice me as well. Please keep up the great work.

Any variegated plant conducts less photosynthesis. White plant tissue isn’t doing a lot of action, they’re the tight-kneed virgins of the plant world. Not to mention the other downfall of celibacy in less photosynthesis means less of all that good energy and nutritious value, too.

I’ve been waiting since 1977 to trot out that little factoid, so please forgive my pedantry.

Patrick: not quite. It’s all about wavelength. The sun puts out electromagnetic energy with a short wavelength, peaking around 600 nanometres; this wavelength slices right through greenhouse gases like CO2 and water vapour, hits the ground, and warms the earth. However, the earth, being a loot cooler than the sun, radiates at much longer wavelengths – the peak is somewhere around 10000-15000 nm nanometres. That wavelength is pretty efficiently absorbed by greenhouse gases, and so can’t escape. Thus, energy can come from the sun to the earth, but can’t easily leave the earth again. Putting reflectors on the ground would shortcut the absorbtion-reemission process, and so energy trying to leave the earth would be of the same wavelength as that coming in, ie one which can pass efficiently through the atmosphere. So it’s not completely stupid.

Jill: quite! I’m not sure why reducing the amount of photosynthesis is a good idea. Sure, less solar energy winds up as heat, but less of it winds up fixing CO2 too. Maybe these alleged scientists have done the sums, and the white leaves more than make up for it. Or maybe they’re thinking of plant varieties with larger leaves too, so what they’re really doing is spreading the same amount of photosynthesis out over a larger area, and so reducing the amount of light that hits the soil, branches, etc, which just turns into heat. In fact, isn’t that exactly what Geoff says?

Hold on, shouldn’t we be absorbing sunlight in solar panels to generate electricity instead of just reflecting it back into space? (Also, re: cow farts, that’s going to be solved by making them fart like kangaroos.)

Not a very bright(!) solution to a sympton. If ever such “strategies” work out we would feel licenced to pollute more, as the problem would seem to be taking care of itself.Like engineered trees that suck more C02, it’d only add to chaos.

Instead of painting the roads white (I shutter at the thought), it would be better to have light colored pavers. I know it sounds crazy to have extensive portions of road paved with pavers, but the idea has surprising merit.

First, instead of having rain water surface flow into storm drains (or flood the street), water would be able to find its way between the cracks and enter into the underground watertable.

Second, pavers slow down traffic and make roads more pedestrian friendly. I’m not sure this trend will keep up, since pavers are now mostly used in high pedestrian areas, so right now we are trained to expect pedestrians when we are driving on pavers. So this might change if pavers became more common.

Third, they are easy to repair and replace. Instead of needing to repave an entire street to fill a single pothole, with pavers all that is required is the pavers to be replaced to fully repair a street.

I’m all for making more reflective cities, but lets not literally white-wash our urban environment.

Pavers for roads are not a good idea, except perhaps in very low traffic areas. The water percolating through them activates the ground underneath in various ways, depending on the nature of the subsurface. It may heave and swell, or wash away, or soften and pothole under the pounding of the traffic. At any rate, keeping the soil moisture level constant beneath a road is one of the major advantages of sealing it.

Some of the climate modelling people have actually played with the orbiting-mirrors idea. IIRC, the upshot is it might reduce the temperature change from greenhouse gasses, but it wouldn’t do much for changing weather patterns. The greenhouse effect alters the way heat moves around the globe, so reducing incoming heat doesn’t really fix the problem.

I suspect that all the white crops in the world won’t make up for the albedo change from melting icecaps.

According to http://en.wikipedia.org/wiki/Solar_energy, “The total solar energy available to the earth is approximately 3850 zettajoules (ZJ) per year,” and, “Worldwide energy consumption was 0.471 ZJ in 2004”.